(a) Field of the Invention
The present invention relates to a filtering device for an aquarium tank. More specifically, the present invention relates to the structure of an improved filtering device in which the cup body can be connected easily and carbon dioxide can be fully dissolved to give a pure, crystal clear conditioned water in the aquarium tank.
(b) Description of the Prior Art
The assembly of a conventional filtering cup for an aquarium is shown in FIG. 1. The upper cup A1 has a tapered bottom edge A11 the diameter of which is smaller than the upper cup A1. A plurality of equidistant notches A12 is located on the bottom edge A11 of the upper cup A1. Each notch A12 has a rib A121 which is used to fit into a corresponding flange A21 of the lower cup A2. The connecting of the upper cup A1 and the lower cup A2 can be accomplished by aligning the flange A21 with the notch A12 together. Either one of the cups can be twisted to allow the flange A21 to fit with the corresponding rib A121. However, the cup body with this kind of connection has the following disadvantages:
(1) The upper cup and the lower cup have to be aligned first, then twisted to connect together. Therefore, the connection can not be accomplished quickly.
(2) The assembly of the upper cup and the lower cup is complex, as can be seen from the aforesaid description.
(3) The cup assembly can nor be rotated freely to change the flow direction of water. Hence, the filtering device in the aquarium can not be operated efficiently.
The structure of a conventional carbon dioxide diffusing tube is shown in FIGS. 2a and 2b. It is made up of two semi-shell bodies 1 and 2 which are clamped together in slots 31 of plastic strips 3 and 4. A carbon dioxide guide tube 7 is coiled inside the tube body, a top cover 5 and a bottom cover 6 are then used to enclose and form the completed carbon dioxide diffusing tube. The inside surfaces of the semi-shell bodies 1 and 2 have a plurality of protruding plates, each of which has an appropriate width and is projected inward. On the exterior surface of the diffusing tube body are the water inlet and outlet connections 16 and 26 with projected rings 12, 13 and 22, 23. The centers of the top cover 5 and bottom cover 6 have punched holes 51 and 61, from which a plastic ring 52 and a plastic gasket 62 are attached to respectively.
Next to the central punched holes 51 and 61 are openings 53 and 63, which are plugged up by pressure relief plugs 54 and 64 respectively.
The carbon dioxide diffusing tube has the following disadvantages:
(1) The tube is made up of two pieces of shell. Therefore, the sealing can never be tight enough to be leak proof.
(2) It is complex and inconvenient to assemble the tube together.
(3) The tube has a simple carbon dioxide guide tube which is coiled inside the diffusing tube body. It does not delay the release of carbon dioxide into water.
(4) The tube can only provide carbon dioxide which will be mixed in water. The tube can not generate oxygen to the aquarium tank. Therefore, its usage is limited.